Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

995
FXUS63 KLOT 251530
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
930 AM CST Sun Jan 25 2026

.KEY MESSAGES...

- Accumulating snow will continue to result in hazardous travel
  conditions today, mainly near Lake Michigan and south/east of
  the I-80/I-55 corridors.

- Locally heavier snowfall rates of 1+"/hour are possible with
  the lake enhanced/lake effect snow.

- Another period of very cold conditions will occur late
  tonight/early Monday morning with wind chills between 20 and
  25 below zero.

&&

.UPDATE...
Issued at 931 AM CST Sun Jan 25 2026

Lake enhanced snow has overperformed overnight with totals of
4-7" observed near Lake Michigan in Cook County. Snow to liquid
ratios have been on the order of 25-40:1 with the lake enhanced
snow. Guidance depicts a strengthening low level convergence
axis this morning with similar moisture and instability
profiles, which would favor a consolidation from a multibanded
structure to a single band or two of more intense lake enhanced
snow. Given the expectation that heavy lake enhanced snowfall
with rates around or just over an inch per hour will continue
across Cook County the remainder of the morning and into at
least the early afternoon, opted to upgrade Cook County to a
winter storm warning. Additional snowfall of 2-5" seems likely
near the lake, which on top of the already 4-7" that has fallen
should leave snowfall totals near the lake in the 6-12" range.

Updated text products will be forthcoming.

- Izzi

&&

.DISCUSSION...
Issued at 340 AM CST Sun Jan 25 2026

Through Tonight:

The national radar mosaic this morning is a sight to behold
with a massive swath of precipitation extending from near the
Mexican border and Gulf Coast up through the Mid-Atlantic. The
northern periphery of the gargantuan precipitation shield
extends into our forecast area, with roughly the southeastern
half of our CWA observing steady, accumulating snowfall at this
time.

Snowfall rates across our southeastern CWA should pick up a bit
over the next few hours as an approaching southern stream
trough and an increasingly coupled jet structure enhance lift
through an exceptionally deep dendritic growth zone. However,
with the strongest forcing focused primarily above the DGZ,
rates here should still only peak at maybe a little more than
0.5"/hour. With the synoptic snow shield still slated to peel
away from west to east this afternoon, our forecast of 4-7"
dry/fluffy storm total snow accumulations for our southeastern
counties with a sharp gradient farther to the northwest thus
still appears to be on track. Therefore, not planning to make any
changes to the going Winter Weather Advisory there with the main
message still being a period of continued hazardous travel
conditions.

Meanwhile, the Arctic air mass in place over a Lake Michigan
with water temperatures in the 30s has allowed for lake
enhancement to occur into Cook County, with a more bona fide
lake effect snow band with embedded mesovortices extending
northward from Lake County, IL up a long ways along the
southeast Wisconsin lakeshore at press time. Earlier last
evening, snowfall rates to around 1"/hour were observed within
the heart of this lake effect band, and would suspect that
similar rates may continue to be observed while the band sits
near the Illinois lakeshore. However, the band has been
struggling to penetrate much more than a few miles inland
(possibly due to the extensive ice coverage in our nearshore
waters), and as such, widely varying snowfall totals will likely
be observed over the span of just a few miles with lower totals
occurring farther away from the lake.

The overall trend for this band should be for it to remain
along or just offshore the southwestern Lake Michigan shoreline
for several more hours this morning before its primary
convergence axis eventually drifts back southward towards Cook
County and then shifts into northwest Indiana, with the band`s
momentum at this point allowing it to penetrate farther inland
after it reaches Lake and Porter counties in northwest Indiana.
For the time that the band stays parallel to the shoreline, its
precise evolution will be difficult to predict beyond 1-2
hours. However, if it manages to sit over the same location for
several hours, then would not be surprised to see some highly
localized 6+" totals be observed. Though, with this still being
an item of lower confidence (and since the spatial footprint of
these higher totals should be quite small and confined to within
a few miles of the lakeshore), will continue to hold off on
issuing a Winter Storm Warning for Lake and Cook counties in
Illinois.

Did give stronger consideration to upgrading Porter County to a
Winter Storm Warning as it looks like there could be a pretty
good 1-3 hour long or so thump of lake effect snow there this
evening with strong omega progged beneath the 7000 ft AGL
inversion as the band shuffles eastward across the county.
Snowfall rates may peak in excess of 1"/hour during this time,
which could add a quick few inches on top of the earlier system
snow accumulation, in addition to making travel more difficult.
Didn`t quite have enough confidence in snowfall totals there
getting much higher than elsewhere to pull the trigger on a
warning upgrade at this time, but will pass my concerns along to
the day shift.

Lastly, northerly winds will strengthen during the day today,
then turn northwesterly this evening, ushering in another period
of cold air advection. With clouds likely to largely clear out
in most spots for tonight as well, temperatures are likely to
fall back below 0F across most of the area once again into
Monday morning. The blustery northwest winds will help yield
minimum wind chills of -20 to -25F across most of the area late
tonight into Monday morning, so have issued another area-wide
Cold Weather Advisory to highlight this.

Ogorek


Monday through Saturday:

Monday morning will start out cold and brisk with a steady WNW/NW
breeze which, when combined with air temperatures in the single
digits, will lead to wind chills in the 15 to 25 below range
through the bulk of the morning. See the short term section
above for specifics on the cold weather headlines. With a robust
shortwave directly overhead to start the day, can`t rule out a
few flurries through the morning and possibly in the afternoon
depending on the expansiveness of any lingering stratus. The
signal for flurries isn`t particularly robust, however, so have
not added a mention to the grids at this point.

The next robust clipper system will descend out of Saskatchewan
on Monday and then across the Upper Great Lakes region Monday
night into Tuesday morning. Seeing generally good agreement on
the handling of this feature, with guidance taking the core of
the most robust mid-level height falls to our north. That said,
the magnitude of large scale forcing is quite robust.

While guidance doesn`t appear to formally produce snow accums
in our area, forecast soundings from various guidance would
support flurries or light snow with saturation down under
850-900 mb, particularly late Monday night through Tuesday
morning across roughly the northeastern half of the CWA and
especially across far northeast Illinois. Thereafter, steepening
0-1 km lapse rates in the wake of the associated surface front
look to drive increasing saturation into the base of a fairly
deep dendritic growth zone late Tuesday morning and afternoon.
Low-level f-gen is generally transient or non- existent,
suggesting the threat for bonafide squalls is low, but seeing a
signal of NW-SE oriented streaks of QPF in some of the guidance
which is likely indicative of isolated-scattered gusty snow
showers through Tuesday morning and early afternoon. At this
time, have not formally added a snow shower mention to the
grids, but if trends continue, will need to consider a weather
mention during this time frame. Can`t totally rule out some
disorganized LES meandering into far NE Porter County Tuesday
afternoon given slightly more NW oriented boundary layer flow,
but the bulk of any lake effect looks to remain decidedly to our
east.

A reinforcing shot of cold air will send low temperatures Tuesday
night back to either side of 0 degrees with colder wind chills
given a steady westerly breeze.

The next robust disturbance arrives late Tuesday night into
Wednesday. Guidance appears to be settling in on a slightly
farther south track at this point, although there`s generally
low confidence this far out with these types of systems. Will be
a period to watch as this would be another instance of light
snow accumulations falling into a very cold airmass where road
treatments would likely be mostly ineffective. Strongest signal
for light snow accumulations into Wednesday afternoon are
roughly south (to well south) of I-80.

Lots of spread in the handling of the general large scale
synoptic pattern by the end of the week. Still seeing a signal
(ephemeral as it may be from run-to-run) of a potentially
interesting set up towards Thursday night - Friday involving an
intense shortwave trough pushing southwestward across the Great
Lakes which would turn the lake effect snow machine back on in
the general region.

Otherwise, continued cold is the message through next week.
Could be some periods where we`re flirting with Cold Weather
headline criteria at times, but nothing to the level of what we
experienced this past Friday/Saturday.

Carlaw

&&

.AVIATION /12Z TAFS THROUGH 18Z MONDAY/...
Issued at 542 AM CST Sun Jan 25 2026

Snow will continue at the Chicago-area terminals today.
Generally prevailing IFR vsbys are expected at ORD, MDW, and
GYY, with more intermittent IFR conditions at DPA. Currently,
lake enhancement is somewhat disorganized, but may become a bit
better organized through the morning. Potential exists for vsbys
to briefly drop under 1 mile at times at ORD, MDW this morning
and early afternoon before activity ends from NW to SE. Continue
to show period of LIFR conditions at GYY where the signal for
heavier lake effect exists this afternoon. At RFD, flurries will
be possible this morning, and perhaps persisting into the early
afternoon.

Winds at ORD/MDW are expected to largely remain N to NNW today,
but at MDW may occasionally flip NE at times. Winds at GYY will
be easterly and will slowly turn northerly through the day.
Gusts will increase this afternoon and snow comes to an end, and
will likely persist into the evening and Monday morning.

Carlaw

&&

.HYDROLOGY...
Issued at 230 PM CST Fri Jan 23 2026

River gauges, reports from local officials, and reports from
trained ice spotters continue to indicate a few ice jams across
the area due to the significant increase in river ice over
recent days. With continued cold weather into next week,
conditions will remain favorable for river ice formation. While
no widespread flooding is expected, localized ice jams may
occur.

- NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Cold Weather Advisory from midnight tonight to noon CST Monday
     for ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-
     ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-
     ILZ039-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.

     Winter Weather Advisory until 6 PM CST this evening for ILZ006-
     ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-
     ILZ106-ILZ107-ILZ108.

     Winter Storm Warning until 4 PM CST this afternoon for ILZ103-
     ILZ104-ILZ105.

IN...Cold Weather Advisory from midnight CST /1 AM EST/ tonight to
     noon CST /1 PM EST/ Monday for INZ001-INZ002-INZ010-
     INZ011-INZ019.

     Winter Weather Advisory until midnight CST tonight for INZ001-
     INZ002.

     Winter Weather Advisory until 9 PM CST /10 PM EST/ this
     evening for INZ010-INZ011-INZ019.

LM...Small Craft Advisory until 6 PM CST Tuesday for Winthrop
     Harbor IL to Gary IN.

     Small Craft Advisory until 6 PM CST Tuesday for Gary to Burns
     Harbor IN-Burns Harbor to Michigan City IN.

&&

$$

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